JP2003277056A - Silica-titania composite film, method for manufacturing the same and composite structural body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica-titania composite film, a method for manufacturing the same, and a composite structural body. <P>SOLUTION: The method for manufacturing a composite film having one layer or a plurality of layers of metal compound films comprising metals of different kinds from titanium and a titanium oxide film as the outermost surface is carried out in the processes of: (1) immersing a substrate having one layer or a plurality of layers of metal compound films comprising metals of different kinds from titanium on its surface in a titanium alkoxide solution; (2) generating low-density titanate colloid having 1 to 30 nm diameter in the liquid by hydrolysis of the titanium alkoxide; and (3) depositing the colloid on the substrate and dehydrating, polymerizing and condensing the colloid to cover the substrate surface with a titanium oxide. The composite film and the composite structural body having a photocatalytic effect are obtained by the above method. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel silica-titania composite film, a method for producing the same, and a composite structure. More specifically, one layer of a metal compound film containing a metal different from titanium as a component is provided. Alternatively, the present invention relates to a composite film having a plurality of layers and a titanium oxide thin film composed of a crystalline anatase phase on the outermost layer, a method for producing the same, and a composite structure.
INDUSTRIAL APPLICABILITY The present invention is useful as a method for producing a composite film in which a uniform and high-quality titania thin film is formed on an arbitrary substrate at a low temperature around 350 ° C. In addition, the composite film uses the photocatalytic activity for environmental purification materials such as wastewater treatment and water purification treatment, anti-fouling film utilizing strong hydrophilicity, coherent coloring film utilizing transparency, photocatalytic activity and transparency. It can be used in various ways as a photocatalytic functional window glass that utilizes the properties that it has and an optical waveguide forming film that utilizes a high refractive index.

[0002]

2. Description of the Related Art Conventional chemical methods for forming a titania thin film on the surface of a substrate include, for example, coating method, sol-gel method,
Known are a chemical vapor transport method, a self-assembled monolayer method, a Langmuir-Brocher method, a sputtering method in a vacuum, and a film forming method by a new chemical reaction different from the sol-gel method. Of these, the coating method is a method in which amorphous or crystalline anatase phase titania fine particles are coated on a substrate together with a binder. In the sol-gel method, a stabilized titania sol partially hydrolyzed by adding a stabilizer to an alcohol solution of titanium alkoxide is prepared, and this is applied as a coating solution to the substrate surface by dipping, spinning, etc., and dried. Is a method of forming a stable amorphous thin film by performing a dehydration polycondensation reaction on the surface of a substrate. In this method, if necessary, the amorphous film is transformed into a crystalline anatase phase by heating and baking.

In the chemical vapor transport method, a vaporized titanium compound is introduced into a substrate fixed in a reaction vessel, and the chemical bond between the surface of the substrate and the gas is used to bring it to the surface of the substrate. This is a method of forming a titania film. At this time, the substrate is heated to form a crystalline anatase phase on the surface of the substrate. The self-assembled monolayer method is similar to the chemical vapor transport method, in which a liquid phase or a vapor phase containing a titanium compound is introduced into a vessel fixed to a reaction vessel,
This is a method of forming a titania film on the surface of a substrate by utilizing the chemical bond between a monomolecular film formed on the surface of the substrate and titanium. The Langmuir-Brocher method forms a film by spreading a hydrophobic liquid in which amorphous titania or crystalline anatase phase fine particles are suspended on standing water and scooping the film on the substrate surface by a method such as dipping. Is the way to do it.

In the sputtering method, the substrate placed in a high-vacuum reaction chamber is heated to increase the reactivity of the substrate surface, and at the same time, a titanium atom or titanium oxide complex is heated in the reaction chamber by a technique such as heating or laser irradiation. Let the molecules evaporate,
Similar to the above chemical vapor transport method, this is a method in which the surface of the substrate is covered with an amorphous titania or crystalline anatase phase. Further, a film forming technique has been developed in which a new coating liquid is prepared by a chemical reaction different from the sol-gel method and the anatase phase titania thin film is formed by baking the coating liquid. In this film forming technology, the coating liquid is applied to the substrate,
After drying, it is said that an anatase phase titania thin film can be obtained by heating at 400 to 500 ° C.

However, the weather resistance of the film produced by the above-mentioned coating method depends on the weather resistance of the binder, and the stronger the photocatalytic activity of the crystalline anatase phase, the faster the deterioration of the binder. The sol-gel method is a method capable of forming a film at a low temperature in a relatively short time, but 1) it takes time to prepare a sol solution for coating, and 2) preparation and coating of the sol solution can be performed in the atmosphere. Difficult, 3) Organic substances are likely to remain in the titania that forms the film, and in order to transfer the phase that forms the film to the crystalline phase anatase in order to express the photocatalytic function, it is usually necessary to bake at a high temperature of 600 ° C. or higher. And 4) there is a problem that the crystallization into the crystalline anatase phase is hindered by the diffusion of the element from the substrate due to the heating.

The Langmuir-Brochier method requires that the surface of the substrate is hydrophobic and has a smooth flat surface. Regarding the chemical vapor transport method and the sputtering method, the size of the substrate is limited as a problem of the methods themselves, and it is difficult to form a film on a surface having a complicated shape, and the possibility of film formation depends on the heat resistance of the substrate. There is a problem that the versatility is poor in that it depends on the properties and the surface characteristics of the substrate. In addition, the reactor is complicated and expensive, and the cost is high. The self-assembled monolayer method has a problem that the procedure for treating the substrate is complicated and the versatility is poor. Further, the film forming technique of anatase phase titania thin film by a chemical reaction different from the sol-gel method requires a heating process at 400 ° C. or higher to obtain the target anatase phase titania thin film. Considering the heat resistance limit, it is desired that the heating temperature be lower.

[0007]

Under the circumstances, the present inventors have drastically solved the above-mentioned problems of the prior art in view of the above-mentioned prior art, and particularly, the low temperature around 350 ° C. In the region, as a result of intensive research aimed at developing a new film forming technology that enables the production of a uniform and high quality titanium oxide film, a silica film is formed on the substrate under specific conditions. Moreover, they have further found that the intended purpose can be achieved by forming a titanium oxide film to construct a silica-titania composite film, and further researches have led to the completion of the present invention. That is, the present invention solves the above-mentioned problems of the prior art, and can form a film on a substrate surface of an arbitrary material having an arbitrary shape and surface characteristics at a much lower temperature range than the conventional method. An object of the present invention is to provide a method for producing a crystalline anatase phase thin film. Another object of the present invention is to provide a uniform and high quality novel photocatalytic highly functional silica-titania composite film produced by the above method. A further object of the present invention is to provide a composite structure having a photocatalytic action, which has the composite film formed by forming the composite film on the surface layer of an arbitrary structure to form a composite.

[0008]

The present invention for solving the above problems is constituted by the following technical means. (1) A method of producing a composite film having one or more metal compound films containing a metal different from titanium as a component, and having a titanium oxide film on the outermost surface, which comprises (a) a titanium alkoxide solution A substrate having one or more layers of a metal compound film containing a metal different from titanium as a component is immersed therein. (B) The titanium alkoxide is hydrolyzed to have a diameter of 1 to 30 nm in the liquid. A method for producing a composite film, which comprises producing a low-density titanic acid colloid, and (c) coating the surface of the substrate with titanium oxide in a liquid by adhesion to these substrates and dehydration polycondensation. (2) The method according to (1) above, wherein the metal compound film containing a metal different from titanium as a component is made of amorphous silica. (3) The method according to (2) above, wherein the film made of amorphous silica is densified by heat treatment. (4) The method according to (1) above, wherein the titanium alkoxide is at least one selected from the group consisting of titanium tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, and titanium tetrabutoxide. (5) The method according to (1) above, wherein the alcohol as the solvent is at least one selected from the group consisting of methanol, ethanol, and isopropanol. (6) The method according to (1) above, wherein the holding temperature of the reaction solution is 0 ° C. or higher and 100 ° C. or lower. (7) Production of a composite film, characterized in that the composite film obtained by the method according to any one of (1) to (6) is heat-treated to transform titanium oxide into a crystalline anatase phase. Method. (8) The method according to (6) above, wherein the heat treatment is performed at 300 ° C. or higher and 1000 ° C. or lower. (9) The composite film obtained by the method according to any one of (1) to (8) above, wherein titanium having a uniform thickness of 0.01 to 100 μm and joined to the surface of the substrate is titanium. A composite film having one or a plurality of metal compound films containing different metals as components, and having a titanium oxide film having a uniform thickness of 0.01-100 μm on the outermost surface. (10) A composite structure having a photocatalytic action, comprising the composite film according to (9) above in a surface layer.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Next, as a result of intensive studies conducted by the present inventors to describe the present invention in more detail, 1) a titanium alkoxide,
Titanium alkoxide hydrolyzed in a solution consisting of alcohol and water forms transient primary particles of titanic acid colloid having a diameter of several tens of nanometers or less. 2) Immersing a substrate in a solution consisting of titanium alkoxide, alcohol and water By doing so, they found that they adhere to the surface of the substrate due to Brownian motion and van der Waals bonds in the solution, and a titania thin film is formed on the surface of the substrate.

Further, the inventors of the present invention 3) place a metal compound film containing a metal different from titanium as a component, for example, an amorphous silica thin film, between the thin film and the substrate, thereby It surely inhibits the diffusion of elements into the titania thin film, thereby enabling the formation of a uniform and high-quality titania thin film. Furthermore, by heating and burning the composite film at around 350 ° C., It was found that it is possible to easily transform the titania, which is the surface layer, into the crystalline phase anatase.

The present invention provides a metal compound film such as an oxide film of a metal other than titanium having a uniform thickness of 0.01 to 100 μm, preferably an amorphous silica, between the surface of a substrate and the titanium oxide. The present invention relates to a composite film having a film, characterized in that a uniform titanium oxide having a thickness of 0.01 to 100 μm forming the outermost layer is a crystalline anatase phase. The present invention relates to a method for producing the composite film, and a highly functional composite structure having the composite film on the surface.

The composite film of the present invention, the outermost layer of which is a crystalline anatase phase titania thin film, basically comprises: a) a single surface or a plurality of layers of a metal compound film of a metal other than titanium, such as a metal oxide. It is produced through the steps of b) coating the substrate of a) with an amorphous titania thin film, and c) firing b) at a temperature of 300 ° C. or higher. A metal compound film of a metal other than titanium, for example, an oxide thin film, is present between the substrate and the titania thin film and inhibits diffusion of elements between the substrate and the titania thin film, thereby providing a uniform and high-quality titania thin film. It is formed for the purpose of enabling the formation.
For these purposes, it is preferable to use a crystalline or silica film, and an amorphous silica film may be used as long as the above object can be achieved. However, the compound is not limited to these, and a compound having low reactivity at high temperature, for example, a silicon compound, preferably silicon nitride, other nitrides, etc., may be similarly used as long as they have the same effect. it can.

For the preparation of the amorphous silica film, preferably, the substrate is immersed in a solution containing silicon alkoxide, alcohol, water and ammonia, and the silicon alkoxide is hydrolyzed to form an amorphous film on the surface of the substrate. Forming a high quality silica film. In this case, it is necessary to keep the reaction liquid in a dynamic state (non-stationary condition). Thereby, the film forming process can be optimized to form a uniform and high-quality silica thin film. When the desired thickness is not achieved, this operation is repeated, the obtained silica film-coated substrate is dried, and if necessary, heated and calcined at a temperature of 300 ° C. or higher and 1000 ° C. or lower, preferably around 350 ° C. A method such as making the silica film have a high density is used. However, it is not limited to these methods. This amorphous silica film is preferably further densified by heat treatment. By forming this highly densified amorphous silica between the substrate and the titania film, it is possible to reliably prevent the diffusion of elements from the substrate to the titania thin film, thereby providing uniform and high quality. It becomes possible to form a highly durable titania film. When such an amorphous silica film is not formed, as shown in Examples described later,
It is difficult to transform the titania film into a high-purity crystalline anatase phase. In the method of the present invention, the formation of the silica film in the method for producing an amorphous silica film is not affected by the size, material, shape of the substrate and hydrophilicity / hydrophobicity of the surface.

Therefore, the formation of the silica-titania composite film of the present invention composed of this silica film and the titania film bonded thereon also requires that the size, material, shape and hydrophilicity / hydrophobicity of the substrate are used. Not affected by gender. As a result, it becomes possible to form the titania film on the surface of the substrate made of any material having any shape and surface characteristics. In the present invention, examples of the base include, but are not limited to, metals, metal oxides, glasses such as soda lime glass and silica glass, plastics such as polyethylene and polystyrene, and silicone rubber. , Any one is acceptable. The surface condition of the substrate may be smooth or uneven. Further, the surface of the substrate may be hydrophilic or hydrophobic, and these properties are not particularly limited.

In the present invention, the formation of the amorphous titania thin film as a step before the formation of the crystalline anatase phase thin film is
By immersing the substrate in a solution composed of titanium alkoxide, alcohol and water and holding it for a predetermined time, the titanium alkoxide is hydrolyzed to form a low density titanic acid colloid having a diameter of 1 to 30 nm in the liquid. It is carried out by forming a titanium oxide film on the surface of the substrate by adhesion to the substrate and dehydration polycondensation, and repeating this operation when the target thickness cannot be achieved by one operation. The formation of the above-mentioned amorphous titania film is due to the fact that transient titanic acid colloidal primary particles having a diameter of several tens of nanometers or less which are generated in a solvent are attached to the surface of the substrate. The formation of a quality titania film depends on the size, material, and
It is not affected by the shape and hydrophilicity / hydrophobicity of the surface. Therefore, for example, the surface of the lower silica film portion can be chemically modified prior to the formation of the amorphous titania film portion.

Whether a uniform and high-quality titania film is formed on the surface of the substrate depends on the polymerization state of titanic acid produced by hydrolysis of titanium alkoxide and the transient titanic acid colloid primary with a diameter of several tens of nanometers or less. It is governed by the kinetics of particle formation, and the amount ratio of titanium alkoxide to water is important in the composition of the prepared solution. Therefore, the concentration of titanium alkoxide is not so important. Basically, when the concentration of titanium alkoxide is decreased, increase the concentration of water and set a long reaction time. , To form a titania film.

In the present invention, as described above, as the titanium alkoxide, one or a mixture of two or more of titanium methoxide, titanium ethoxide, titanium isopropoxide and titanium butoxide is used. Preferably, titanium tetraethoxide or titanium tetraisopropoxide is used. As the solvent, one or a mixture of two or more of methanol, ethanol, isopropanol and butanol is used, and preferably ethanol or isopropanol is used. The concentration range is preferably 0.0
1 to 1.0 mol / l, and the desirable concentration range is
It is 0.025 to 0.1 mol / l.

Water is necessary to cause hydrolysis and to form a titanic acid colloid. The amount thereof is in the range of 1 to 100 by molar ratio with respect to the titanium alkoxide. The holding temperature of the reaction solution in the film formation process may be below freezing, but is preferably 0 ° C or higher and 100 ° C or lower. More preferably, it is around room temperature. In this case, the reaction is preferably carried out in a closed container for the purpose of preventing volatilization of the solvent.

The above reaction may be carried out by allowing it to stand, but it is preferable to keep the reaction solution in a dynamic state in order to obtain a uniform film. As a method therefor, circulating the solution, The reaction is preferably performed in a shaking environment (non-stationary condition) by vibrating the substrate, shaking the reaction tank, or the like. In the method of the present invention, the rate of film formation can be expressed as a logarithmic function of the retention time. Further, since the film formation is due to the transient adhesion of primary particles of colloidal titanic acid colloid having a diameter of several tens of nanometers or less, which is generated by the hydrolysis of titanium alkoxide, the starting time of immersion of the substrate and the holding time should be set appropriately. By setting, the film thickness can be strictly controlled. The amorphous titania film obtained in the present invention can be transformed into a highly pure and high density crystalline anatase phase by firing at 300 ° C. or higher and 1000 ° C. or lower, preferably around 350 ° C. At this time, the OH and alkyl groups contained in the film structure can be removed, and thus the outermost layer can form a composite film having a highly pure crystalline anatase phase.

[0020]

In the present invention, in the titanium alkoxide solution, a metal compound film containing a different metal different from titanium as a component,
For example, a metal oxide film, preferably a silica film on the surface 1
A substrate having a layer or a plurality of layers is dipped, and the titanium alkoxide is hydrolyzed to generate a low-density titanic acid colloid having a diameter of 1 to 30 nm in the liquid, and adhesion to these substrates and dehydration polycondensation are performed in the liquid. By optimizing these in the process of forming the titanium oxide film on the surface of the substrate, it becomes possible to form a uniform and high-quality titania film on the substrate. In the present invention, it is possible to reliably inhibit the diffusion of the element from the substrate to the titania thin film by forming the silica film portion in the lower layer of the titania film portion, thereby,
It becomes possible to form a uniform and high-quality and highly durable titania film.

The method of the present invention makes it possible to prepare a composite having the above-mentioned titania film formed on the surface of a substrate of any material having any shape and surface characteristics. In addition, the above-mentioned composite body is above 300 ℃ and below 1000 ℃, preferably 350 ℃
By firing in a low temperature region before and after, it is possible to transform into a highly pure crystalline anatase phase. The transient titanic acid generated by the hydrolysis of titanium alkoxide is repeatedly condensed and redissolved in the liquid, and among the transient titanic acid colloids formed by condensation, they collide with each other and have a surface area / volume ratio. Only the smaller one escapes re-dissolution and becomes the solid phase. This transient titanic acid colloid constantly repeats production and dissolution during the progress of the reaction, and its size is proportional to the degree of supersaturation of dissolved titanic acid. According to the discovery of this fact, the present invention has realized that a titania film can be formed on the surface of a substrate even if the initiation and duration of immersion of the substrate are arbitrarily set while the reaction is in progress.

[0022]

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the following examples. (1) Formation of silica thin film In the present examples, A soda lime glass plate was used as the substrate. The silica film was formed by the following procedure. A solution prepared by dissolving silicon tetraethoxide in ethanol so that the reaction would be 0.22 mol / l, and a solution prepared by dissolving these in ethanol so that water was 6.0 mol / l and ammonia 2.0 mol / l during the reaction. Was prepared and the substrate was immersed in the former. The former container was shaken to keep the reaction liquid in a dynamic state, and the latter was added thereto. Then, the container was sealed with a film and kept at 20 ° C. while shaking.

After 2 hours, the substrate was taken out,
0.648 m of water for 120 ml of ethanol
1-washed, dried at 70 ℃, 350
It was baked at 48 ° C. for 48 hours. The thickness of the obtained silica film,
As a result of examination with an atomic force microscope (AFM), the film thickness is 0.1.
It was 2 μm. The surface roughness of the silica film is RMS roughness 1
was nm.

(2) Formation of Titania Film Next, a titania film was formed by the following procedure. Titanium ethoxide 1.35g and isopropanol 100ml
And a solution of 0.648 ml of water and 20 ml of isopropanol were prepared, and the substrate was immersed in the former. After shaking the former container and shaking the reaction solution and adding the latter to it, the container was sealed with a film,
Hold at 20 ° C. with shaking.

After 4 hours and 8 hours, the substrate was taken out and dried at 70 ° C. for 2 hours. As a control, 1) a soda lime glass substrate having no silica thin film on the surface, and 2) a soda lime glass substrate having a silica thin film on the surface but not subjected to firing at 350 ° C. after forming the silica thin film and before forming the titania thin film, The same process was performed on the. Then, these samples were heated and baked at 350 ° C.

(3) A part of the resulting unfired titania thin film was peeled off and the film thickness was measured by an atomic force microscope. As a result, the film thickness was 0.09 μm and 0.18 μm for the films subjected to the film forming treatment for 4 hours and 8 hours, respectively. Next, the presence or absence of a crystal phase was examined with an X-ray diffraction device. As a result, no diffraction line due to the crystal phase was observed in any of the samples. Next, the heat-fired sample was examined by an X-ray diffractometer for the presence or absence of a crystal phase. As a result, a silica thin film was present between the soda lime glass and the titania thin film, and the titania film thickness was 0.18 μm, and The diffraction line due to the crystalline anatase phase was observed only for the silica thin film that had been baked at 350 ° C (Fig. 2).

No diffraction line due to the crystalline anatase phase was observed for the silica thin film having a titania film thickness of less than 0.09 μm even after being subjected to firing at 350 ° C. Similar results were obtained for this silica thin film when the firing conditions were 450 ° C. and 10 hours. From these experiments, the thicker the silica thin film is, the more the diffusion of elements from the substrate is hindered. Therefore, even if the titania film is thin, it can be transformed into the anatase phase. It turned out that the phase can be changed.

Example 2 A silica film and a titania film were formed in the same manner as in Example 1 above. When the thickness of the silica film was 0.24 μm, the titania film formation time was 4 hours. Even when the titania film thickness was 0.09 μm, the diffraction line due to the crystalline anatase phase was observed in the film that had been baked at 350 ° C. for 48 hours by setting the silica film film thickness to 0.24 μm. (Figure 3).

Example 3 In the same manner as in Example 1, except that titanium isopropoxide was used as the titanium alkoxide and a silica glass plate was used instead of the silica film, the titania film formation time was 6 hours, and the titania film was formed. Diffraction lines due to the crystalline anatase phase were also observed for the film having a film thickness of 0.14 μm. The firing temperature at this time was 300 ° C., which was lower than those in Examples 1 and 2.

Example 4 A titania film was formed on a substrate by the same method as in Example 1 above, and the film thickness of the titania film when a silicon plate and a soda lime glass plate were used as the substrate was examined. As a result, it was found that the titania film thickness is expressed by the following equation as a logarithmic function of the reaction time t (minute) (FIG. 4). On silicon plate: d (nm) = 232 log (t)-
451 On soda lime glass plate: d (nm) = 243 lo
g (t) -475

Example 5 In Example 1 above, the solvent was ethanol, the hydrophilic substrate was a silicon plate, and the strongly hydrophobic substrate was 1H, 1H, 2H, 2H-perfluorodecyltr having a strongly hydrophobic surface.
Example 1 except that a silicon plate chemically modified (fluorine treated) with an imethoxysilane monomolecular film was used as a substrate
A titania film was formed in the same manner as in. As a result of measuring the film thickness of the obtained titania film by measuring with an atomic force microscope, it was found that the film thickness was expressed by the following equation as a logarithmic function of the reaction time t (min) (FIG. 5). On untreated silicon plate: d (n
m) = 141.89 log (t) -131.17 on hydrophobically treated silicon plate: d (nm) = 127.23 log
(T) -119.33

Example 6 The silica film thickness produced in the above Example 1 was 0.12.
The light transmittance in the ultraviolet-visible light region was measured for soda lime glass in which a composite film having a thickness of 0.1 μm and a titania film thickness of 0.18 μm and a crystalline anatase phase was bonded to one surface. As a result, it was found that the decrease in the light transmittance over the entire visible light region was a low value of about 10% (FIG. 6). Further, when the photocatalytic activity of this composite film was investigated by a conventional method, it was found that the crystalline titania film had an excellent photocatalytic action.

[0033]

As described in detail above, the present invention relates to a silica-titania composite film, a method for producing the same, and a composite structure, and the present invention has the following special operational effects. It (1) According to the method for producing a silica-titania composite film of the present invention, a crystalline anatase phase thin film is formed on a substrate having an arbitrary surface state and an arbitrary surface shape if the heat resistant temperature of the substrate is 300 ° C. or higher. can do. (2) This crystalline anatase thin film is used for environmental purification such as wastewater treatment and water purification treatment utilizing its photocatalytic activity, surface decoration such as antifouling coating utilizing strong hydrophilicity and interference coloring film utilizing transparency. It can be suitably used for applications, such as photocatalytic functional window glass that utilizes both photocatalytic activity and transparency, for improving the living environment, and industrial applications such as an optical waveguide forming film that uses a high refractive index. (3) It is possible to provide a composite structure having a photocatalytic action in which the composite film is formed on the surface layer.

[Brief description of drawings]

FIG. 1 shows an outline of a method for producing a composite membrane of the present invention.

FIG. 2 shows the results of X-ray powder diffraction of the composite film (the diffraction line at the diffraction angle of 25 ° indicates the presence of a crystalline anatase phase).

FIG. 3 shows the results of X-ray powder diffraction of the composite film (the diffraction line at the diffraction angle of 25 ° indicates the presence of a crystalline anatase phase).

FIG. 4 shows the relationship between the thickness of a titania film and the reaction time.

FIG. 5 shows the relationship between the film thickness of a titania film formed on hydrophilic and hydrophobic substrates and the reaction time.

FIG. 6 shows the results of measuring the light transmittance of glass in the ultraviolet-visible light region.

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Claims (10)

[Claims] 1. A method for producing a composite film having one or a plurality of metal compound films containing a metal different from titanium as a component and having a titanium oxide film on the outermost surface, comprising: (1) titanium A substrate having one or a plurality of metal compound films containing a metal different from titanium as a component is immersed in an alkoxide solution. (2) The titanium alkoxide has a diameter of 1 to 1 in the liquid by being hydrolyzed. (3) A method for producing a composite film, which comprises producing a low-density titanic acid colloid having a thickness of 30 nm, and (3) coating the surface of the substrate with titanium oxide in a liquid by adhesion to these substrates and dehydration polycondensation. . 2. The method according to claim 1, wherein the metal compound film containing a metal different from titanium as a component is made of amorphous silica. 3. The method according to claim 2, wherein the film made of amorphous silica is densified by heat treatment. 4. The method according to claim 1, wherein the titanium alkoxide is at least one selected from the group consisting of titanium tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, and titanium tetrabutoxide. 5. An alcohol as a solvent is methanol,
The method according to claim 1, wherein the method is at least one selected from the group consisting of ethanol and isopropanol. 6. The holding temperature of the reaction solution is 0 ° C. or higher and 10
The method according to claim 1, which is 0 ° C or lower. 7. A method for producing a composite film, which comprises subjecting a composite film obtained by the method according to claim 1 to heat treatment to transform titanium oxide into a crystalline anatase phase. . 8. The method according to claim 6, wherein the heat treatment is performed at 300 ° C. or higher and 1000 ° C. or lower. 9. A composite film obtained by the method according to any one of claims 1 to 8, which is bonded to the surface of a substrate and has a uniform thickness of 0.01 to 100 μm, which is different from titanium. 1. A composite film comprising one or more metal compound films containing the metal as a component, and a titanium oxide film having a uniform thickness of 0.01-100 μm on the outermost surface. 10. A composite structure having a photocatalytic action, comprising the composite film according to claim 9 on a surface layer.